I have a 38' MH and a 24' trailer. I'm 68' bumper to bumper, IIRC, which means I'm illegal in PA and other places with a 65' or less total length limit.
I've never seen a "You can do it, but you need a CDL" exemption... I think being over length is being over length regardless of license grade, but different states have different rules (and may not have reciprocity, so it may not matter that I'm legal in OH), so do your own research.
I've not talked to an RV'er that's been caught over length, so I don't know what the punishment is. The impression I get is that this isn't something the cops / DOT folks are looking for.